Wouldn't it be easier (and perhaps cheaper in the long run) to just mod out one of those mini fridges?
I mean set it up under your desktop, there would be I think plenty of room for a pair of towers inside on the bottom. Run a couple of holes out the top for wireing, set the thermostat at like 25 degrees and voila.
You now have a cool computer, and an handy spot to keep a few cold drinks close by.
No modifications needed for your computer at all.
Might want to add an external cd/dvd drive to save opening the fridge.